P1.01-23 - High PD-L1 Expression is Less Common Than Expected Among Advanced NSCLC in Brazil. Are We Missing the Target? (ID 13620)

Immune checkpoint inhibitors improved outcomes of patients with advanced non-small cell carcinoma (NSCLC). In clinical trials 30% of patients had programmed death receptor ligand-1 (PD-L1) expression above 50% and this frequency may vary through different regions of the world. We aim to describe the real world dada on prevalence of PD-L1 expression, EGFR mutation and ALK translocation in Brazil.

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Method

Immunohistochemistry (IHC) for PD-L1, antibody 22C3 PharmDx Dako, was performed in 5 laboratories in Brazil from Aug/2017 through Apr/2018 in cases of advanced NSCLC considered for treatment with immunotherapy. Mutations in EGFR (exons 18 to 21) by Cobas®(Roche), NGS, or other non-specified tests and ALK by IHC (antibodies 5A4 or D5F3) or FISH (Vysis System) were performed in non-squamous cases. All analyses were with SAS (version 9.4). P-values <0.05 were deemed to be statistically significant.

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Result

PD-L1 expression was assessed in 1382 samples of advanced NSCLC. The median age was 67 years, and 55.6% were male. 56.6% had adenocarcinoma, 18.0%, squamous, 20.7%, non-specified NSCLC, 2.5%, other histologies, 1.9%, missing. Of the 1380 cases, 17.4% presented PD-L1 expression ≥50%, 25.4%, 1-49%, and 57.1% <1%. The histological subtype showed association with the expression of PD-L1 (p=0,0431). In adenocarcinoma, 60.7% had no PD-L1 expression, 23.1%, had 1-49%, and 16.1%, ≥50%, while in squamous, 47.3% had no PD-L1 expression, 30.5% had 1-49%, and 22.0%, ≥50%. Among 885 samples with EGFR data, 10.9% were mutated. Both sex and histology showed association with EGFR mutation (p=0.0410 and p<0.0001). Among the men, 9.7% were mutated, while 13,4% of women were mutated. 16.4% of adenocarcinoma and 3.1% of squamous had EGFR mutation. In 855 samples with ALK data, 3.5% were rearranged. ALK rearrangement was associated with sex and age (p=0.0388 and p=0.0088) and was 2.2% in men and 4.8% in women. The group with age <50 had a higher prevalence of ALK rearrangement (8.6%). Among 735 patients without EGFR mutations or ALK rearrangements, 16.8% had PD-L1 ≥50% and 24.0% had 1-49%.

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Conclusion

Our results indicate a lower overall prevalence of PD-L1 expression in advanced NSCLC in Brazil as compared with clinical trial data. Among other potential factors, inadequate sample handling, pre-analytical issues, or epidemiology of the biomarker may impact PD-L1 expression. Prevalence of EGFR mutations and ALK translocations was within the range of prior publications in the country. Further regional and institutional analysis will be presented to better characterize the variations in prevalence of these biomarkers outside clinical trials.

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